Big Babies
One of the common things that parents, and care providers worry about are babies that are estimated to be ‘big’. In the UK we class babies larger than 8lbs 13oz to be big or macrosomic. However, the only way to accurately measure how big a baby is, is to weigh them after they have been born.
Palpation of the stomach varies from midwife to midwife and isn’t terribly accurate based on the position of the baby each time. Scans to measure the size of baby can be very inaccurate and the weight estimation can be out by 15-20%. Therefore a baby that is estimated to be 8lbs can be anything from 6lbs 13oz to 9lbs 3oz. I f used regularly throughout pregnancy, then they are more accurate for plotting the growth of a baby but as a one off near the end of pregnancy they don’t tell us a great deal.
As many care providers will still suggest induction or caesarean for a suspected big baby, despite it going against the NICE guidance, growth scans in late pregnancy are associated with a higher chance of induction or caesarean. If you would like to accept a growth scan that is recommended to you during pregnancy, you are able to decline any recommendations given based on your baby being estimated large.
You can, choose to go ahead with any recommendations if that is what you prefer or decline the growth scan altogether. You may also wish to ask for another scan a few days later in order to see if the two measurements are the same before making your decision.
The NICE guidelines state “In the absence of any other indications, induction of labour should not be carried out simply because a healthcare professional suspects a baby is large for gestational age (macrosomic)”.
In a study on size estimations in the U.S, 1 in 3 of the women in the study were told their baby was ‘too big’. The average weight at birth of the babies in the ‘too big’ category was actually 7lbs 130z.
Another U.S study looked at the outcomes of people who were estimated to have a big baby and compared them to the outcomes of people who had a big baby unexpectedly. The study showed that the first group were 3x more likely to have an induction or caesarean and 4x more likely to have severe perineal tearing and postpartum haemorrhage.
This shows us that some of the things we worry about occurring due to big babies are not caused by big babies themselves, rather they may be caused by the management often recommended when they are suspected to be large, or how that may impact confidence.
One of the things that is often discussed with a bigger than average baby is them becoming ‘stuck’ as they’re born or Shoulder Dystocia. Looking into the statistics around shoulder dystocia and you will see that although spoken about often, it is still a small percentage of babies who experience this (0.7% or 1 in 150) and that it affects small babies as well, just larger babies slightly more often.
Shoulder dystocia rarely leads to any adverse effects to baby and is more likely to require a simple change in position as baby comes out to give them room to move out. In order to prevent litigation against them, some care providers like to place great emphasis on the (slight) increased risk to larger babies in order to ensure parents are informed of the possibility. Seeking out the evidence and figures on shoulder dystocia can be really reassuring.
Resources
NICE Guidelines- Inducing Labour
Sarah Ockwell -Smith - Big babies, the curse of mis-diagnosing a macrocosmic infant
EBB- Evidence on: InducItion of Caesarean for a Big Baby
Evidence Based Birth Big babies handout
Midwife Thinking: The risk of care provider fear
Cochrane: Induction of labour for big babies
Why Induction Matters by Rachel Reed
Inducing Labour: Making Informed Decisions by Sara Wickham